Laser beam machining method

ABSTRACT

A method of laser beam machining which has a simple construction and which is capable of suitably processing a part to be processed by means of laser beams is provided. A plurality of laser diode arrays  3  are stacked and disposed in such a manner as to allow radiation of laser beams in the direction of a width W of a part  1  to be processed. Each of the laser diode arrays  3  is controlled such that outputs  2 R,  2 L of laser beams with which the part  1  to be processed is irradiated in its width (W)-wise marginal portions  1 R,  1 L become higher than an output  2 C of laser beams with which the part  1  to be processed is irradiated in its width (W)-wise central portion  1 C. While the part  1  to be processed is irradiated with the laser beams with the distribution of energy thus changed, the laser beams are displaced relatively in the longitudinal direction of the part  1  to be processed.

TECHNICAL FIELD

The present invention relates to a method of laser beam machining, andmore particularly to a method of subjecting a part to be processed to apredetermined processing such as padding, welding, or hardening throughradiation of laser beams.

BACKGROUND ART

For example, if a part to be processed is subjected to padding by meansof laser beams (laser cladding) to form a cladding layer, it iscustomary that a powdery cladding material be applied to or deposited onthe surface of a base material and that the cladding material beirradiated with laser beams. The laser beams that have been radiated aremultiplicatively reflected in the cladding material and are therebyabsorbed while being attenuated, thus heating the cladding material andwelding it to the base material. It is to be noted herein that thedistribution of energy of generally employed laser beams with which apart to be processed is irradiated is either defocused and adapted forGaussian mode (single mode) or adapted for multiple mode so as to ensurethat the laser beams exhibit an intensity of a predetermined levelcontinuously over a certain width (although it is in fact difficult tomaintain the intensity of the laser beams at the predetermined level).

As a more concrete example of performing padding by means of such laserbeams, it is known to supply a wear-resistant and corrosion-resistantcladding material that is different from a material for an intake orexhaust valve body of an engine or its valve seat portion (basematerial) to the surface of the base material through a nozzle or thelike with a view to enhancing the wear resistance and corrosionresistance of the valve body or the valve seat portion, irradiate thecladding material with laser beams, weld the cladding material to thevalve body or the valve seat portion (base material), and clad it with acladding layer.

One of the arts applicable to such an example is disclosed in JapanesePatent Application Laid-Open No. HEI 9-239574 as a method ofmanufacturing an engine valve. This publication mentions “that a methodof manufacturing an engine valve (by cladding it with a cladding layerthrough radiation of laser beams) requires uniformly heating a powderymaterial for padding (cladding material) over the entire region in theradial direction of a valve body and that if a base material is forexample heated partially and excessively, the phenomenon of dilution,namely, penetration of constituents of the base material through apadding material occurs as a result of fusion of the base material andmakes it impossible for the padding material (cladding material) toexhibit its inherent properties such as wear resistance or causesinconveniences such as incomplete welding, underfill, fusion sag, andthe like of the padding material” (see paragraph 0003 of thispublication).

As a problem to be solved, this publication mentions “that the basematerial of the valve body at the beginning of padding is at a roomtemperature, that the heat of laser beams is conveyed to the basematerial at a position to be padded later as the operation of paddingbased on radiation of laser beams proceeds, that the later the basematerial is padded at a certain position, the higher the temperature ofthe base material at the position becomes, and that the temperature ofthe base material almost at the end of padding is higher than thetemperature of the base material at the beginning of padding” (seeparagraph 0005 of this publication). As a means for solving the problem,Japanese Patent Application Laid-Open No. HEI 9-239574 discloses “amethod of manufacturing an engine valve wherein a groove portion isformed in a valve body in its region that serves as a valve face andwherein laser beams are displaced relatively in the circumferentialdirection of the groove portion so as to perform padding while thepowdery material for padding that has been supplied to the grooveportion is being irradiated on the surface of its powder layer with thelaser beams, characterized in that distribution of output energy of thelaser beams is controlled such that a marginal portion at the time ofeach padding operation is maintained at a substantially constanttemperature from the beginning of padding to the end of padding” and “amethod of manufacturing an engine valve wherein a groove portion isformed in a valve body in its region that serves as a valve face andwherein laser beams are displaced relatively in the circumferentialdirection of the groove portion so as to perform padding while thepowdery material for padding that has been supplied to the grooveportion is being irradiated on the surface of its powder layer with thelaser beams, characterized in that the surface of a powder layer isirradiated with the laser beams whose spot diameter has been narroweddown to a value smaller than the width of the groove portion, that thelaser beams having the spot diameter thus narrowed down are oscillatedin the radial direction of the valve, and that the width of oscillationis reduced after padding has been started”.

Furthermore, as an effect of the construction as described above, thispublication mentions “that since the marginal portion of each paddingposition can be maintained at a suitable temperature from the beginningof padding to the end of padding, it is possible to inhibit the paddingmaterial from decreasing in wear resistance or corrosion resistance orfrom undergoing incomplete welding or underfill due to dilution of thebase material in the marginal portion that has a low heat capacity,perform padding uniformly and with good quality over the entire region,and provide a high-quality engine valve” (see paragraph 0035 of thispublication).

As is also shown in FIG. 12, a device for performing padding by means oflaser beams thus narrowed down (adapted for Gaussian mode) comprises aparabolic mirror 31 for condensing oscillated laser beams, anoscillating mirror 32 for oscillating laser beams 30 that have beencondensed and adapted for Gaussian mode in accordance with a width W ofa cladding material 1 that has been deposited on the surface of a basematerial 5 as a part to be processed, and a driving means (not shown)for driving the oscillating mirror 32 in a fluctuating and reciprocatingmanner, such as a galvanometer or the like. Furthermore, in general, anozzle 7 for supplying shielding gas to the cladding material 1 aroundits region irradiated with laser beams is provided.

In the case where a valve seat or the like is thus subjected to apredetermined processing such as padding or the like by means of thelaser beams 30 that have been adapted for Gaussian mode, it has beencustomary to displace the laser beams 30 relatively in the longitudinaldirection (or in the circumferential direction) of the part 1 to beprocessed while oscillating them in the direction of the width W (or inthe radial direction) of the part 1 to be processed.

However, as described above, in the case where padding is performed bymeans of laser beams, laser beams that have been radiated aremultiplicatively reflected by a cladding material and absorbed whilebeing attenuated, whereby the cladding material is heated and welded toa base material. Hence, if the cladding material that has been depositedwith different thicknesses is irradiated with laser beams of the sameintensity, it exhibits a higher degree of multiplicative reflection oflaser beams and thus absorbs a greater amount of the radiated laserbeams in its region that has been deposited to a great thickness. Thus,as compared with the region that has been deposited to a smallthickness, the region that has been deposited to a great thicknessexhibits a higher degree of distribution of heat input and is morelikely to be heated. On the other hand, the cladding material that hasbeen supplied to and deposited on the surface of the base material bymeans of a nozzle or the like is generally thick in its widthwisecentral portion and thin in its widthwise marginal portions.Accordingly, in the case of irradiating the cladding material that hasbeen supplied to the surface of the base material from the nozzle withlaser beams of a uniform intensity, the cladding material is heatedexcessively in its widthwise central portion that has been deposited toa great thickness so that dilution of the base material tends to occur,and the cladding material is heated insufficiently in its widthwisemarginal portions that have been deposited to a small thickness so thatincomplete welding tends to occur.

The conventional art disclosed in the aforementioned Japanese PatentApplication Laid-Open No. HEI 9-239574 takes into account the fact thatthe heat of laser beams during the operation of padding is conveyed tothe base material at its position to be padded later so that the basematerial rises in temperature, and is designed to adjust thedistribution of output energy in the processing (longitudinal) directionof the laser beams such that the marginal portion of the engine valve tobe padded is maintained at a substantially constant temperature from thebeginning of padding to the end of padding. This conventional art doesnot consider the difference in distribution of heat input in thedirection of the width of the cladding material.

Further, as described above, this publication mentions that the artdisclosed therein requires uniformly heating the entire region in thedirection of the width of the cladding material. For this purpose, laserbeams are oscillated with respect to the cladding material in the radialdirection (the direction of the width) of the valve. Therefore, acladding layer 1′ is formed with an undulant surface or meandrousmarginal portions 1 e′. The problem is that the cladding layer 1′ cannotbe formed smoothly. In the case where a valve body or a valve seat issubjected to laser cladding, the surface of a cladding material that hasbeen formed to ensure sealing properties during abutment of the valvebody on the valve seat is ground or subjected to other processings.However, if the cladding layer 1′ is formed with an undulant surface ormeandrous marginal portions, the amount of the cladding layer 1′ to beground or subjected to other processings is increased. The problems arethat the method becomes time-consuming and laborious and that a certainamount of the cladding material 1 is wasted.

Furthermore, in the case where the laser beams 30 that have been adaptedfor Gaussian mode are oscillated within a predetermined width of thepart to be processed, there is a problem of dependency of thedistribution of heat input on the diameter of the condensed laser beams30. That is, as shown in FIG. 13, it is assumed for example that thepart to be processed has the width W of 5 mm and that the condensedbeams 30 have a diameter of 3 mm, 2 mm or 1 mm. If the condensed beams30 have a diameter of 3 mm, they overlap with one another at the centerin the direction of the width W of the part 1 to be processed, so thatthe distribution of heat input is biased toward the center in thedirection of the width W of the part 1 to be processed. If the condensedbeams 30 have a diameter of 2 mm, the part 1 to be processed isirradiated with the beams in its width (W)-wise marginal portions over alonger period than in its width (W)-wise central portion, so that moreheat is inputted to the width (W)-wise marginal portions of the part 1to be processed than to the width (W)-wise central portion of the part 1to be processed. If the condensed beams 30 have a diameter of 1 mm, thepart 1 to be processed is irradiated with the beams in its width(W)-wise marginal portions over a much longer period than in its width(W)-wise central portion, so that the distribution of heat input isbiased toward the width (W)-wise marginal portions of the part 1 to beprocessed and that the amount of heat inputted to the width (W)-wisecentral portion of the part 1 to be processed is insufficient. That is,the problem is that the distribution of heat input cannot be stabilized.In the case of padding, if the distribution of heat input is biasedtoward a certain portion, the phenomenon of dilution, namely,penetration of the base material 5 through the cladding material 1′occurs, and it becomes impossible to perform the function of enhancingwear resistance and the like of the valve seat or the like. That is, theproblem is that the part to be processed is heated excessively and canno longer be processed as originally intended. Further, in the case ofpadding, if the intensity of laser beams is lowered with a view topreventing the part to be processed from being heated excessively, thecladding material cannot be welded to the base material. That is, theproblem is that the amount of heat inputted to the part to be processedbecomes insufficient so that the part to be processed can no longer beprocessed as originally intended.

In addition, since the device for oscillating laser beams is designed todrive the oscillating mirror 32 in a fluctuating and reciprocatingmanner, it is complicated in structure and control logics. Anotherproblem is that the maintenance operations for removing dirt from theoscillating mirror 32 etc. are laborious.

On the other hand, in the case where the part to be processed isirradiated with laser beams that have been adapted for multiple mode, inorder to maintain the intensity of the laser beams at a predeterminedlevel continuously in the width direction, it is necessary to averagethe intensity of the laser beams at the predetermined level in the widthdirection. The problem is that the laser beams decrease in energyefficiency. Another problem is that it is difficult to actually maintainthe intensity of the laser beams at the predetermined level. Inaddition, as is apparent from a comparative example shown on the rightside of FIG. 6(a), even in the case of radiating laser beams that havebeen adapted for multiple mode, the cladding material 1 is heatedexcessively in its width (W)-wise central portion that has beendeposited to a great thickness as described above, so that acorresponding portion of the base material 5 is heated up to the extentof causing dilution (see a comparative example shown in FIG. 6(b)).Further, the cladding material 1 is heated insufficiently in its width(W)-wise marginal portions that have been deposited to a smallthickness, so that incomplete welding is caused. As a result, as isapparent from a comparative example shown in FIG. 6(c), the apex of thecladding layer 1′ that has been formed is bulgy and biased toward alocation which is heated excessively and to which a great amount of heatis inputted. Thus, in the case of padding a valve seat or the like, thecladding layer 1′ is not smooth enough to be welded to the base material5. The problems are that the amount of the cladding layer 1′ to beground later is increased and that the valve seat becomes incapable ofperforming its inherent function.

Such problems ascribable to the dependency of the distribution of heatinput on the position in the direction of the width of the part to beprocessed occur not only in the case where padding such as lasercladding or the like is performed but also in the case where laser beamwelding, laser beam hardening, or the like is performed.

The present invention has been made as a solution to the aforementionedproblems. It is an object of the present invention to provide a methodof laser beam machining which has a simple construction and which iscapable of suitably processing a part to be processed by means of laserbeams.

SUMMARY OF INVENTION

In order to achieve the object stated above, the method of laser beammachining according to the present invention as set forth in claim 1 ischaracterized in that a plurality of laser diode arrays are disposed insuch a manner as to allow radiation of laser beams in the direction of awidth of a part to be processed and that each of the laser diode arraysis controlled in accordance with the direction of the width of the partto be processed so as to shape laser beams and irradiate the part to beprocessed with the laser beams.

In order to achieve the object stated above, the method of laser beammachining according to the present invention as set forth in claim 2 isbased on the present invention as set forth in claim 1 and ischaracterized in that each of the laser diode arrays is controlled andlaser beams are shaped such that distribution of energy is changed inaccordance with a width position of the part to be processed.

In order to achieve the object stated above, the method of laser beammachining according to the present invention as set forth in claim 3 isbased on the present invention as set forth in claim 2 and ischaracterized in that the distribution of energy is changed bycontrolling each of the laser diode arrays and shaping the laser beamssuch that laser beams with which the part to be processed is irradiatedin its widthwise marginal portions exhibit a higher intensity than laserbeams with which the part to be processed is irradiated in its widthwisecentral portion.

In order to achieve the object stated above, the method of laser beammachining according to the present invention as set forth in claim 4 isbased on the present invention as set forth in any one of claims 1 to 3and is characterized in that laser beam machining is a processing whichis selected from padding, welding and hardening and to which the part tobe processed is subjected.

According to the present invention as set forth in claim 1, the laserdiode arrays are disposed in such a manner as to allow radiation oflaser beams in the direction of the width of the part to be processed,and the laser beams are displaced relatively in the longitudinaldirection of the part to be processed while being radiated so as toperform a predetermined processing. At this moment, each of the laserdiode arrays is controlled to ensure that the laser beams are radiatedin a state of being shaped in accordance with the direction of the widthof the part to be processed.

The present invention as set forth in claim 2 is based on the presentinvention as set forth in claim 1 and is designed such that each of thelaser diode arrays is controlled and the laser beams are shaped so as tochange the distribution of energy in accordance with the width positionof the part to be processed.

The present invention as set forth in claim 3 is based on the presentinvention as set forth in claim 2 and is designed such that each of thelaser diode arrays is controlled to change the distribution of energysuch that laser beams with which the part to be processed is irradiatedin its widthwise marginal portions exhibit a higher intensity than laserbeams with which the part to be processed is irradiated in its widthwisecentral portion. Thereby, the part to be processed is uniformly andsuitably processed in its widthwise marginal portions that cannot beprocessed easily and in its widthwise central portion that can beprocessed easily.

The present invention as set forth in claim 4 is based on the presentinvention as set forth in any one of claims 1 to 3 and is designed suchthat the laser beams are radiated in a state of being shaped inaccordance with the direction of the width of the part to be processedso as to optimally perform the processing that has been selected frompadding, welding and hardening.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory view showing one embodiment of the presentinvention.

FIG. 2 is a perspective view of a laser diode array.

FIG. 3 is an explanatory view showing how parallel laser beams areradiated by a microlens provided in the laser diode array.

FIG. 4 is an explanatory view showing another embodiment of the presentinvention.

FIG. 5 is an explanatory view showing still another embodiment of thepresent invention.

FIG. 6 is an explanatory view showing in a contrastive manner (a) arelation between intensities of laser beams and positions in the widthdirection, (b) distribution of temperatures in a base material, and (c)shape of a cladding layer that has been formed, as to the case of thepresent invention in which laser beams are radiated with variabledistribution of energy and to a comparative example in which laser beamsare radiated with invariable distribution of energy.

FIG. 7 is an explanatory view showing one embodiment of the presentinvention in which laser beams are radiated with variable distributionof energy in the case where a work having a uniform thickness ishardened.

FIG. 8 is an explanatory view showing another embodiment of the presentinvention in which laser beams are radiated with variable distributionof energy in the case where a work having a uniform thickness ishardened.

FIG. 9 is an explanatory view showing another embodiment of the presentinvention in which laser beams are radiated with variable distributionof energy in the case where a work having different thicknesses ishardened.

FIG. 10 is an explanatory view showing one embodiment of the presentinvention in which laser beams are radiated with variable distributionof energy in the case where a work having a uniform thickness and avariable speed of weld penetration is butt-welded.

FIG. 11 is an explanatory view showing one embodiment of the presentinvention in which laser beams are radiated with variable distributionof energy in the case where a work having different thicknesses and auniform speed of weld penetration is butt-welded.

FIG. 12 is an explanatory view of a conventional laser beam machiningdevice in which laser beams are oscillated.

FIG. 13 is an explanatory view showing how the distribution of heatinput changes depending on the diameter of condensed laser beams in theconventional laser beam machining device in which laser beams areoscillated.

DETAILED DESCRIPTION

Hereinafter, a method of laser beam machining according to oneembodiment of the present invention in the case of padding will bedescribed in detail with reference to FIGS. 1 to 6. It is to be notedherein that like reference symbols denote like or correspondingelements.

The method of laser beam machining according to the present invention isgenerally designed such that a plurality of laser diode arrays 3 aredisposed in such a manner as to allow radiation of laser beams in thedirection of a width W of a part 1 to be processed, that the laser diodearrays 3 are controlled so as to shape laser beams 2 in such a manner asto allow the laser beams 2 to be emitted in the direction of the width Wof the part 1 to be processed, and that the laser beams 2 thus shapedare displaced in the longitudinal direction of the part 1 to beprocessed while being radiated. Furthermore, this method is designedsuch that the part 1 to be processed is irradiated with the shaped laserbeams 2 while the laser diode arrays 3 are controlled in such a manneras to change the distribution of energy in accordance with the positionin the width direction of the part 1 to be processed. Especially in thecase of padding or the like, outputs from the laser diode arrays 3 arecontrolled and the distribution of energy is changed such thatintensities 2R, 2L of laser beams with which the part 1 to be processedis irradiated in its width (W)-wise marginal portions 1R, 1L becomehigher than an intensity 2C of laser beams with which the part 1 to beprocessed is irradiated in its width (W)-wise central portion 1C. It isto be noted that the part to be processed in this embodiment is acladding material 1 that has been deposited linearly on the surface of abase material 5. By irradiating the cladding material 1 with the laserbeams 2, a cladding layer 1′ welded to the surface of the base material5 is formed.

First of all, the construction of a laser beam machining device that isemployed to implement the method of the present invention will bedescribed. The laser beam machining device employed in the presentinvention comprises a laser beam source 6 and a control means (notshown). The laser beam source 6 is composed of the laser diode arrays 3that are disposed such that laser beams can be radiated in the directionof the width W of the part 1 to be processed. The control means controlsthe laser diode arrays 3 such that the laser beams 2 that have beenshaped in accordance with the direction of the width W of the part 1 tobe processed can be radiated. In the case where padding is performed toform the cladding layer 1′, the laser beam machining device of thisembodiment comprises a nozzle (not shown) for supplying the part 1 to beprocessed with the powdery cladding material 1 making the cladding layer1′ and a nozzle 7 (see FIG. 12) for supplying the surroundings of thecladding material 1 to be irradiated with the laser beams 2 withshielding gas. For example, if an intake or exhaust valve body of anengine or its valve seat portion is subjected to padding in thisembodiment, powder of an alloy composed of such materials as can enhancewear resistance and corrosion resistance when the cladding material 1 iswelded to the valve body or the valve seat portion is used as thecladding material 1.

The laser diode arrays 3 is made, for example, from gallium arsenidesemiconductor laser devices. The electric current supplied to each ofthe laser diode arrays 3 is controlled, whereby the intensity of beamsradiated therefrom can be adjusted. As shown in FIGS. 2 and 3, aplurality of laser emission ports 3 a are provided on one face of eachof the laser diode arrays 3. In addition, a microlens 8 is secured tothe face where the laser emission ports 3 a are provided. For example,laser beams having a length s of about 100 μm and a width t of about 1.0μm are emitted from each of the laser emission ports 3 a. Because themicrolens 8 is provided in front of the laser emission ports 3 a,parallel laser beams having a length S of about 1 cm and a width T ofabout 1 mm can be radiated. Unlike the laser beams adapted for multiplemode as described in the description of the background art, the laserbeams 2 can be radiated while their energy is distributed in a clearlystepped manner, and can be stabilized at a certain level as shown inFIG. 1 and the like.

In this embodiment, as shown in FIG. 1, the laser diode arrays 3 thusconstructed are disposed above the cladding material 1 in the directionof the width W, thus constituting the laser beam source 6. A controldevice (not shown) is connected to each of the laser diode arrays 3,which is supplied with an electric current that has been controlled soas to allow radiation of laser beams having a predetermined output. Thelaser beam source 6 is set such that the laser beams 2 having a totaloutput of, for example, about 4 kw can be radiated when the suppliedelectric current is controlled so as to assume 100%. A condensing lens 9is interposed between the laser beam source 6 and the cladding material1. Distances among the laser beam source 6, the condensing lens 9 andthe cladding material 1, that is, focal distances can be adjustedrelatively at need. The number of the laser diode arrays 3 disposed inthe direction of the width W of the cladding material 1 that has beendisposed linearly is set such that the width of the laser beams 2 withwhich the cladding material 1 is irradiated becomes at least equal to orgreater than the width W of the cladding material 1 that has beendeposited linearly. In the embodiment shown in the drawings, the laserdiode arrays 3 are disposed such that the width of the laser beams 2with which the cladding material 1 is irradiated becomes equal to thewidth W of the cladding material 1 that has been deposited linearly (seethe laser diode arrays 3 indicated by solid lines in FIG. 1). It is alsopossible to dispose the laser diode arrays 3 such that the laser beams 2having a width equal to or greater than the width W of the claddingmaterial 1 can be radiated (see laser diode arrays 3′ indicated byalternate long and two short dashes lines in FIG. 1), to provide aconstruction in which electric power is supplied only to a requirednumber of the laser diodes 3 in accordance with the width W of thecladding material 1, and to thereby achieve general-purpose propertiesthat make it possible to deal with the part 1 to be processed with avariable width.

When padding is performed according to the method of laser beammachining of the present invention using the laser beam machining deviceconstructed as described above, the cladding material 1 having thepredetermined width W is supplied linearly from the nozzle (not shown),and the laser beams 2 that have been shaped by the control device (notshown) in accordance with the direction of the width W of the claddingmaterial 1 are radiated and displaced relative to the cladding material1 in the longitudinal direction thereof. It is to be noted herein thatthe cladding material 1 that has been deposited linearly is thick in itswidth (W)-wise central portion and thin in its width (W)-wise marginalportions.

It is to be noted herein that the laser diode arrays 3 disposed in thedirection of the width W of the cladding material 1 as shown in FIG. 1are classified into a group 3C for irradiation of the width (W)-wisecentral portion of the cladding material 1 with laser beams having anoutput 2C and groups 3R, 3L for irradiation of the width (W)-wisemarginal portions of the cladding material 1 with laser beams havingoutputs 2R, 2L. The control device (not shown) performs control suchthat the electric current supplied to the laser diode arrays 3 of thegroup 3C for irradiation of the width (W)-wise central portion 1C of thecladding material 1 becomes lower than the current supplied to the laserdiode arrays 3 of the groups 3R, 3L for irradiation of the width(W)-wise marginal portions 1R, 1L of the cladding material 1. Forexample, the control device (not shown) performs control such that theoutput from the laser diode arrays 3 of the group C for irradiation ofthe width (W)-wise central portion 1C of the cladding material 1 assumes50% and that the output from the laser diode arrays 3 of the groups 3R,3L for irradiation of the width (W)-wise marginal portions 1R, 1L of thecladding material 1 assumes 90%. Thus, as shown in FIG. 1, the claddingmaterial 1 is irradiated such that beams with which the claddingmaterial 1 is irradiated in its width (W)-wise central portion 1Cexhibit a low (weak) intensity 2C and that beams with which the claddingmaterial 1 is irradiated in its width (W)-wise marginal portions 1R, 1Lexhibit high (strong) intensities 2R, 2L respectively. The width(W)-wise central portion 1C of the cladding material 1 has beendeposited to a great thickness and can be processed easily, whereas thewidth (W)-wise marginal portions 1R, 1L of the cladding material 1 havebeen deposited to a small thickness and cannot be processed easily. Thatis, the shaping of the laser beams 2 in the direction of the width W ofthe part 1 to be processed according to the present invention issynonymous with the shaping of the laser beams 2 not only in such amanner as to perform control for allowing radiation of the laser beams 2having a width substantially equal to the width W of the part 1 to beprocessed but also in such a manner as to allow radiation of laser beamshaving suitable intensities in the direction of the width W of the part1 to be processed, namely, in such a manner as to allow the part 1 to beprocessed to be heated with suitable distribution of heat input. As aresult, as shown in FIG. 6(b) as the present invention, the claddingmaterial 1 is heated substantially uniformly in the direction of thewidth W thereof and is welded to the surface of the base material 5without being diluted, so that the smooth cladding layer 1′ is formed.On the other hand, as shown in FIG. 6(b) as the comparative example thatis distinct from the present invention, if the laser beams 2 having auniform intensity are radiated from the laser diode arrays 3 in thedirection of the width of the cladding material 1, the width (W)-wisecentral portion 1C of the cladding material 1 is heated excessively anddiluted with the base material 5, and the width (W)-wise marginalportions 1R, 1L of the cladding material 1 are heated insufficiently andcannot be welded sufficiently as in the case of the background art.Also, the cladding layer 1′ is formed such that its apex is bulgy andbiased toward a location which has been heated excessively and to whicha great amount of heat is inputted.

If the cladding material 1 is welded annularly to the base material 5such as a valve body or a valve seat portion, the laser beams 2 arerelatively displaced in the circumferential (longitudinal) directionwhile being radiated in the radial (width) direction. In this case, theradially inside marginal portion (1R or 1L) of the cladding material 1and the radially outside marginal portion (1L or 1R) of the claddingmaterial 1 are different from each other in circumferential speed duringdisplacement in the circumferential direction. Therefore, if the laserbeams 2 having a uniform intensity are radiated, the radially inside andoutside marginal portions of the cladding material 1 are also differentfrom each other in distribution of heat input. In such a case, controlis performed such that the beams with which the radially inside marginalportion (1R or 1L) is irradiated exhibit a higher (stronger) intensitythan the beams with which the radially outside marginal portion (1L or1R) is irradiated. For example, it is possible to perform control suchthat the output from the laser diode arrays 3 of the group 3R forirradiation of the cladding material 1 in its radially outside one 1R ofthe marginal portions assumes 90% and that the output from the laserdiode arrays 3 of the group 3L for irradiation of the cladding material1 in its radially inside one 1L of the marginal portions assumes 70%.Alternatively, it is also possible to perform control such that theoutput from the laser diode arrays 3 of the group 3L for irradiation ofthe cladding material 1 in its radially inside one 1L of the marginalportions assumes 50% just like the output from the laser diode arrays 3of the group 3C for irradiation of the cladding material 1 in itscentral portion.

Further, the method of laser beam machining according to the presentinvention should not be limited to cases where the laser beam machiningdevice constructed as described above is employed. For example, as shownin FIG. 4, the laser beam machining device can be constructed such thata collimation lens 8′ is provided instead of the microlens 8 in front ofthe emission ports 3 a of the laser diode arrays 3, that the collimationlens 8′ converts the laser beams 2 emitted from the emission ports 3 aof the laser diode arrays 3 into the parallel laser beams 2, and thatthe cladding material 1 that has been supplied to the surface of thebase material 5 is then irradiated via the condensing lens 9 with thelaser beams 2 that have been controlled so as to exhibit a predeterminedintensity.

Furthermore, as shown in FIG. 5, the laser beam machining device can beconstructed, for example, such that each of transmission fiber cables 10is connected to a corresponding one of the emission ports 3 a of thelaser diode arrays 3 and that the cladding material 1 that has beensupplied to the surface of the base material 5 is irradiated via thecollimation lens 8′ and the condensing lens 9 with the laser beams 2that have been controlled so as to exhibit a predetermined intensity. Inthis case, the laser beam source 6 constructed by arranging the laserdiode arrays 3 does not need to be disposed above the cladding material1 and in parallel with the direction of the width W of the claddingmaterial 1. Thus, the degree of freedom in designing the laser beammachining device is increased.

The method of laser beam machining according to the present inventionshould not be limited to the embodiment in which padding is performed asdescribed above, and is also applicable to laser beam machining of othertypes such as laser beam welding and laser beam hardening. In this case,it is not indispensable to perform shaping so as to radiate the laserbeams 2 such that the outputs 2R, 2L for the part 1 to be processed inits width (W)-wise marginal portions 1R, 1L become higher than theoutput 2C for the part 1 to be processed in its width (W)-wise centralportion 1C. That is, it is also possible to perform shaping so as toradiate the laser beams 2 such that the output 2C for the width (W)-wisecentral portion 1C becomes higher than the outputs 2R, 2L for the width(W)-wise marginal portions 1R, 1L.

Hereinafter, embodiments of the present invention in which laser beamwelding (FIGS. 7 to 9) and laser beam hardening (FIGS. 10 and 11) areperformed will be described. It is to be noted in the followingdescription that elements identical with or corresponding to those inthe aforementioned case of padding are denoted by the same referencesymbols and will not be described again.

FIGS. 7 to 9 show a case where a work 5 is hardened in its part 1 to beprocessed which has a predetermined width. These drawings schematicallyshow the distribution of the energy of laser beams to be radiated isdepicted above the surface of the part 1 to be processed and thedistribution of the heat input resulting from the laser beams isdepicted below the surface of the part 1 to be processed. As for theformer, the output of the laser beams at each width (W) position isrepresented by a height corresponding to the intensity of the laserbeams. As for the latter, each of substantially isothermal areas isrepresented by a line.

FIG. 7 shows a case where the laser beams with which the work 5 isirradiated in the part 1 to be processed are shaped and radiatedaccording to three output groups for the widthwise central portion 2Cand the widthwise marginal portions 2R, 2L. In this embodiment, the work5 to be hardened has a uniform plate thickness or a uniform wallthickness.

It is to be noted herein that the heat inputted to both the marginalportions of the part 1 to be processed generally tends to be lower thanthe heat inputted to the central portion of the part 1 to be processedif the laser beams are radiated in the direction of the width W withuniform distribution of energy. Hence, if laser beams are radiated so asto harden the part 1 to be processed in both the marginal portionsthereof at a predetermined temperature, the amount of heat inputted tothe central portion of the part 1 to be processed may become excessiveto the extent of causing penetration.

However, in the case of the method according to this embodiment of thepresent invention, the electric current to be supplied to each of thelaser diode arrays 3 is controlled and set such that the output 2C ofthe laser beams for the central portion of the part 1 to be processedbecomes lower (weaker) than the outputs 2R, 2L of the laser beams forboth the marginal portions of the part 1 to be processed. Thus, heat isinputted uniformly to the work 5 in the part 1 to be processed, so thatthe work 5 is hardened uniformly without causing a problem ofpenetration or the like.

In the case where the work 5 having a uniform thickness is hardened, themethod of the present invention should not be limited to theaforementioned embodiment in which the laser beams are shaped accordingto three groups. For example, as shown in FIG. 8, the electric currentto be supplied to each of the laser diode arrays 3 may be controlled andset such that the laser beams are shaped and radiated according to evenmore groups 2C1, 2C2, 2R1 or 2L1, and 2R2 or 2L2 or the like so as toincrease the output gradually from the widthwise central portion towardthe widthwise marginal portions.

FIG. 9 shows a case of the embodiment in which the work 5 havingdifferent thicknesses is hardened in the part 1 to be processed. Theelectric current to be supplied to each of the laser diode arrays 3 iscontrolled and set in such a manner as to achieve uniform distributionof heat input, whereby laser beams with which the part 1 to be processedis irradiated are shaped such that their outputs 21 to 26 are graduallylowered in a direction from the thicker side to the thinner side. Thus,even the work 5 having different thicknesses can be hardened uniformlywithout causing a problem of penetration or the like.

FIGS. 10 and 11 show a case where works 5A, 5B are butt-welded and acase where works 5C, 5D are butt-welded, respectively. Each of thesedrawings shows the distribution of the energy of laser beams to beradiated is depicted above the surfaces of connecting ends 1A, 1B or 1C,1D of both the works and the distribution of the degree of penetrationresulting from the laser beams is depicted below the surfaces of theconnecting ends 1A, 1B or 1C, 1D of both the works. As for the former,each of the outputs 2A, 2B or 2C, 2D of the laser beams with which acorresponding width (W) position is irradiated is represented by aheight corresponding to the intensity of the laser beams. As for thelatter, those regions of the works 5A, 5B or 5C, 5D which have beenfused by being irradiated with the laser beams are represented.

Although the works 5A, 5B shown in FIG. 10 are substantially equal inthickness, they are made from materials that are different in speed ofweld penetration (depth of weld penetration). For example, one of theworks 5A is made from iron, and the other work 5B is made from aluminum.

In general, if works made from different materials are irradiated withlaser beams of the same output, the speed of weld penetration of thework made from aluminum is higher than that of the work made from iron.Hence, if the work 5A made from iron and the work 5B made from aluminumare butted against each other and welded to each other by beingirradiated with laser beams of the same output, incomplete welding suchas insufficient fusion of the work 5A or meltdown of the work 5B iscaused.

However, in the case of the method according to the embodiment of thepresent invention shown in FIG. 10, the electric current to be suppliedto each of the laser diode arrays 3 is controlled and set so as to shapethe laser beams such that the output 2B of the laser beams with whichthe work 5B is irradiated at its connecting end 1B becomes lower(weaker) than the output 2A of the laser beams with which the work 5A isirradiated at its connecting end 1A. Thus, the connecting end 1A of thework 5A and the connecting end 1B of the work 5B are melt to asubstantially equal depth at a substantially equal speed, and areconnected to each other without causing incomplete welding.

The works 5C, 5D shown in FIG. 11 are equal in speed of weldpenetration, for example, because they are made from the same material.However, the works 5C, 5D are different in thickness. That is, one ofthe works 5C is thinner than the other work 5D.

In general, if works made from the same material and having differentthicknesses are irradiated with laser beams of the same output, thespeed of weld penetration in the thicker one of the works is lower thanthe speed of weld penetration in the thinner one of the works. Hence, ifthe thinner work 5C and the thicker work 5D, which are made from thesame material, are butted against each other and welded to each other bybeing irradiated with laser beams of the same output, incomplete weldingsuch as meltdown of the thinner work 5C and insufficient fusion of thethicker work 5D is caused.

However, in the case of the method according to the embodiment of thepresent invention shown in FIG. 11, the electric current to be suppliedto each of the laser diode arrays 3 is controlled and set so as to shapethe laser beams such that the output 2C of the laser beams with whichthe work 5C is irradiated at its connecting end 1C becomes lower(weaker) than the output 2D of the laser beams with which the work 5D isirradiated at its connecting end 1D. Thus, the connecting end 1C of thework 5C and the connecting end 1D of the work 5D are suitably melt to asubstantially equal depth at a substantially equal speed, and areconnected to each other without causing incomplete welding.

In order to shape laser beams in accordance with the direction of thewidth W of the part to be processed, the present invention may bedesigned not only to control the electric current to be supplied to eachof the laser diode arrays but also to additionally employ other means(not shown) such as an integration mirror and the like.

Further, the present invention may employ a plurality of laser diodearrays that are stacked via insulating materials (spacers).

INDUSTRIAL APPLICABILITY

The present invention as set forth in claim 1 can provide a method oflaser beam machining which is capable of suitably processing a part tobe processed by means of laser beams, on the basis of a simpleconstruction wherein a plurality of laser diode arrays are disposed soas to allow radiation of laser beams in the direction of the width ofthe part to be processed and wherein each of the laser diode arrays iscontrolled in accordance with the direction of the width of the part tobe processed so that laser beams are shaped and that the part to beprocessed is irradiated with the laser beams.

The present invention as set forth in claim 2 is based on the presentinvention as set forth in claim 1 and designed such that each of thelaser diode arrays is controlled and laser beams are shaped so as tochange the distribution of energy in accordance with the width positionof the part to be processed and to thereby irradiate the part to beprocessed with the laser beams with suitable distribution of energy.Thus, the present invention as set forth in claim 2 can provide a methodof laser beam machining which is capable of suitably processing a partto be processed.

The present invention as set forth in claim 3 is based on the presentinvention as set forth in claim 2 and designed such that thedistribution of energy is changed by controlling each of the laser diodearrays and shaping the laser beams such that laser beams with which thepart to be processed is irradiated in its widthwise marginal portionsexhibit a higher intensity than laser beams with which the part to beprocessed is irradiated in its widthwise central portion. Thus, thepresent invention as set forth in claim 3 can provide a method of laserbeam machining which is capable of uniformly and suitably processing apart to be processed in its widthwise marginal portions that cannot beprocessed easily and in its widthwise central portion that can beprocessed easily.

The present invention as set forth in claim 4 is based on the presentinvention as set forth in any one of claims 1 to 3 and can provide amethod of laser beam machining which is capable of optimally performinga processing that has been selected from padding, welding and hardening.

1. A method of laser beam machining: comprising the steps of: disposing a plurality of laser diode arrays in a direction of a width of a part to be processed in such a manner as to allow radiation of laser beams in the direction of the width of a part to be processed, and controlling each of the laser diode arrays and shaping the laser beams such that laser beams in which the part to be processed is irradiated in its widthwise marginal portions exhibit a higher intensity than laser beams with which the part to be processed is irradiated in its widthwise central portion.
 2. The method of laser beam machining according to claim 1, wherein laser beam machining is a processing which is selected from padding, welding and hardening and to which the part to be processed is subjected.
 3. The method of laser beam machining according to claim 1, wherein shaping the laser beams includes distributing an intensity of the laser beams in a stepwise manner along a width of the part to be processed. 